This invention pertains to a draw frame for textile slivers and is more particularly directed to a method and a device for pressing down the upper rolls onto the respective lower rolls of the drawing unit which is composed of serially arranged roll pairs formed of upper and lower rolls. During operation the upper rolls are pressed against the respective lower rolls by loaded pressing elements in pressing arms. In the inoperative state the upper rolls are relieved of pressure by the pressing arms.
During operation, the pressing arms are closed and the pressing devices press the upper rolls onto the associated lower rolls of the drawing unit. In case the drawing frame is at a standstill particularly for a longer time period, the pressing arms are opened to thus release the upper rolls from the pressing forces for protecting the roundness of the rolls and their elastic coating against deformation. In a known arrangement the pressing arms are pivoted open manually while the upper rolls remain stationarily positioned on the lower rolls. In such an arrangement the upper rolls exert a pressure on the lower rolls by their weight. Since the slivers are positioned between the upper and lower rolls, the upper rolls, in their idle state, exert a pressure on the slivers. During operation, particularly at high sliver speeds of 1,000 m/min and above, the rolls heat up substantially. Frequently the fibers contain substances which become sticky when heated, for example, honeydew in cotton and reviving agents in chemical fibers. Occasionally the draw frame is at a standstill for a period which is longer than, for example, the time required for coiler can replacements at the output end of the draw frame. Such longer periods may occur, for example, in case of sliver rupture or in case of coiler can replacements at the input end of the draw frame, during operational disturbances and the like. During such longer standstill periods, particularly as the upper output roll (or rolls) press against the sliver situated between the roll pair the earlier noted substances become sticky by heating. As a disadvantageous result, the slivers adhere firmly mostly to the upper rolls and, when operation resumes, the slivers are entrained in a circular path by the rotating roll and are thus wound thereon. This is a highly undesirable phenomenon which results in substantial operational disturbances since the draw frame must be immediately stopped and the wound sliver manually removed from the roll. Such a defect may often not be immediately eliminated which leads to significant delays and thus to downtimes in the production.